Pasture establishment and fertiliser requirements on rehabilitated land after opencast coal mining in New Zealand

摘要

Existing pasture establishment practices to rehabilitate land after opencast mining in the Waikato coal fields area of New Zealand were examined and compared with an alternative method involving different pasture mixtures, seeding rates, and lime and fertiliser requirements. Pasture establishment and production, botanical composition changes, and plant and soil nutrient status were measured during a 2‐year field trial. Highly significant pasture responses were obtained to increased fertiliser inputs. Heavy rates of fertiliser (1000 kg ha−1superphosphate) were required to raise Olsen P soil levels during the establishment phase whereas half that rate was found to be sufficient for the maintenance phase. An improved seed mixture, containing superior pasture cultivars, established more quickly and out‐yielded the existing seed mixture by 58. The two seed mixtures responded differently to sowing rates; the higher rate increased pasture yields of the improved pasture species but decreased the existing seed mix yields. Liming at 5 t ha−1significantly increased soil pH and clover content and reduced pasture manganese concentrations from possibly toxic levels. Nitrogen concentrations in pastures were below optimum throughout the trial and the strategic use of nitrogen fertiliser is recommended as a useful management option.